EP1906066A1 - Valve, in particular for ultra high purity gas containers - Google Patents

Abstract

The valve has a holding ring (70) surrounding an annular seal (64) in a circumferential manner and comprising a radial lip (72) supported on an outer edge of a front end face of the seal. The seal has an outer annular shoulder on the edge of the front end face of the seal. The radial lip of the holding ring has an annular bead (76) facing the shoulder of the seal. The ring is fixed to an open/close element (32) by a leaktight outer circumferential weld (77), so that the bead passes axially into the shoulder of the seal to compress it.

Description

Technical area

The present invention relates to a valve, in particular for cylinder (or cylinder) of gas or liquefied gas. This valve is particularly well suited for applications using ultra pure gases.

State of the art

The increasing use of specialty gases and the high level of purity demanded today by some industries is reflected in a continuing effort by manufacturers of valves, valves and other gas distribution equipment to improve the quality and the integrity of their products.

For the semiconductor industry, for example, high quality gas distribution systems have been developed because the presence of impurities in the gases could irretrievably affect the electrical properties of the components and thus also affect the production efficiency. In addition, these gases are expensive, highly reactive, corrosive and / or toxic and it is therefore imperative to have suitable and reliable equipment.

Despite these efforts, the design of some valves conventionally used in high purity applications is not considered fully satisfactory. Such a valve comprises for example a valve body provided with a gas passage in which is arranged a sealing seat. The end of the lower rod acts as a sealing head and comprises for this purpose an annular seal of polymer material mounted in an annular groove. The annular groove is delimited on the inner side by a free end of the lower rod and on the outer side by a retaining ring.

Types of fixtures are generally used for the maintenance of the joint. In a first case, the retaining ring comprises on its face in contact with the annular seal a series of teeth intended to bite the seal and thus retain it, the seal being inserted into force in the annular groove. Alternatively, the annular seal is placed around the free end of the lower rod, and the ring is then fixed by screwing or crimping to the lower rod so as to circumferentially surround the annular seal. In this case, the retaining ring may comprise a radial flange engaging the outer edge of the front face of the polymeric seal.

As noted earlier, high purity (HP) and ultra high purity (UHP) applications involve increased requirements for purity and watertightness. However, in the designs mentioned above, the presence of teeth involves abrasion of the seal, which generates particles, and causes dead volumes (volumes not occupied by the seal). For a screwed ring, it is not possible to guarantee sealing at the threads, and the friction on the threads also generate particles. Furthermore, when screwing the ring, it can exert torsional forces on the annular seal which can deform. Finally, in the crimping assembly it is not possible to guarantee the tightness of the assembly or to precisely control the maintenance of the annular seal.

Thus, current designs include dead volumes and potential leakage areas, which are not desirable for pure and ultra pure gas applications.

Object of the invention

The object of the present invention is to provide a valve better suited to the requirements of HP and UHP applications. According to the invention, this objective is achieved by a tap according to claim 1.

General description of the invention

According to the invention, a valve for compressed or liquefied gas comprises a valve body provided with a gas flow passage extending between an inlet port and an outlet port; and a first sealing seat in said gas passage. A closure member associated with the first sealing seat has a free end provided with a shoulder. An annular seal of polymer material is mounted on the free end of the closure member, the annular seal having a front face facing the first seal seat and a rear end face resting on the shoulder of the seal body. shutter. A retaining ring attached to the closure member circumferentially surrounds the annular seal and comprises a radial rim bearing on the outer edge of the front end face of the annular seal. The shutter member is adapted to be moved axially towards the first seat in a first sealing position, wherein the annular seal is pressed against the first seat so as to ensure a main seal of the valve.

According to an important aspect of the invention, the annular seal comprises an outer annular shoulder bordering its front end face; and the rim of the retaining ring carries an annular bead facing the outer annular shoulder of the annular seal. The retaining ring is attached to the closure member by means of a sealed outer circumferential weld, so that the annular bead penetrates axially into the outer annular shoulder of the annular seal to compress it.

In the valve according to the invention, the annular seal is confined in an annular groove delimited by the free end and the shoulder of the closure member and the retaining ring. Such confinement makes it possible to control the creep / deformation of the annular seal during its compression on the sealing seat.

In addition, the annular bead provided on the rim of the retaining ring makes it possible to overcompress the annular seal in the annular groove and to occupy the entire volume, thus avoiding the dead volumes that can trap gas. It will be noted here that the dimensions of the annular seal and the cavity are preferably chosen so that the compression forces are initially generated by the annular bead. Thus, it is during the mounting of the retaining ring that we will compress the seal by means of the annular bead. A Another advantage of the annular bead is to punctually create a large compression zone with the annular seal, which forms a sealing barrier.

Finally, the attachment by welding on the entire circumference and in a sealed manner is a guarantee of sealing at the rear of the annular seal which can not be reached by crimping or screwing. The laser is particularly preferred for the welding operation, for reasons of accuracy, heat control and practices. The welding can be done with or without material input. Other welding techniques for performing precise welds can also be employed, such as by electron beam. It will also be noted that the fixing of the solder retaining ring allows a simple assembly of the ring on the body of the closure member essentially without exerting constraints on the annular seal other than that generated by the annular bead, thus avoiding its damage during assembly.

According to one embodiment, the free end of the closure member comprises a radial end projection penetrating radially into an annular shoulder inside the annular seal. The free end of the closure member may have a truncated conical shape of the shoulder in the direction of the radial projection. This radial end projection serves two purposes: (1) when mounting the annular seal, it keeps it in place; (2) Once the retaining ring is welded, it produces a sealing barrier effect similar to that obtained at the annular bead on the rim of the retaining ring. In this variant, the annular seal is confined in the annular groove, which comprises at its inlet two sealing barriers to prevent the passage of gas towards the rear of the annular seal.

Preferably, the outer circumferential weld between the retaining ring and the closure member is made axially recessed relative to the shoulder. For this purpose, the closure member may comprise a peripheral annular shoulder surrounding the shoulder on which the annular seal rests, but in axial recess with respect thereto, the retaining ring being then welded to the closure member at this peripheral annular shoulder. This axial offset makes it possible to perform the welding at a certain distance from the joint to prevent it being damaged by heat.

The valve body advantageously comprises a second sealing seat surrounding the passage, the shutter body being movable axially beyond the first sealing position in a second sealing position, in which said free end comes sitting on this second seat so as to achieve with the latter a metal seal. The presence of this second seat is of particular interest in UHP applications where the gases are expensive and often toxic, because it allows to close the valve by a metal seal, even if the annular seal is degraded or displaced (by abrasion or by excessive tightening forces), or disappears (eg as a result of combustion).

It will be understood that such a second sealing seat is normally arranged so as to be surrounded by the first sealing seat, and the portion of the free end coming to sit on the second sealing seat has a cross section greater than the section of the gas passage at said second sealing seat.

In practice, it can be provided that the axial displacement required to bring the shutter member from the first sealing position to the second sealing position is less than 0.3 mm, preferably of the order of 0 , 1 mm.

Control of the shutter member is conventionally effected by means of a control head comprising an axial control rod for transmitting at least one axial actuating force to the shutter member. The control head may be of the manually or automatically controlled type (eg pneumatic or solenoid).

According to one embodiment, the shutter member comprises an axial rod portion for its operation, which can be integral with the control rod of the control head, or coupled thereto. A rigid coupling separable between the control rod and said axial rod portion of said Shutter member is preferred for flexibility of use.

The valve according to the invention is therefore particularly advantageous in ultra-high purity applications in particular because of the good sealing of its closure member without dead volumes. For use as a gas cylinder valve, the valve body is adapted to be attached to a bottle and the inlet port of the passage channel typically opens into the bottle. This valve can however also be used as a valve / gate valve in a gas distribution system (fluid). In this case, the valve body will preferably be adapted so that the inlet and outlet ports are connectable to the pipes or other elements of the gas distribution system.

Description of the drawings

• FIG.1: une vue en coupe longitudinale d'un mode de réalisation préféré d'un robinet selon l'invention, dans une position d'étanchéité principale de l'organe d'obturation ;
• FIG.2: une vue en coupe longitudinale de l'organe d'obturation ;
• FIG.3: une vue agrandie du détail A ;
• FIG.4: une vue en coupe explosée de l'organe d'obturation ;
• FIG.5: une vue en coupe de l'organe d'obturation sans la bague de maintien.

Other features and features of the invention will become apparent from the detailed description of an advantageous embodiment presented below, by way of illustration, with reference to the accompanying drawings. These show:

• FIG.1: a longitudinal sectional view of a preferred embodiment of a valve according to the invention, in a main sealing position of the closure member;
• FIG. 2 is a view in longitudinal section of the shutter member;
• FIG. 3: an enlarged view of detail A;
• FIG. 4: an exploded sectional view of the shutter member;
• FIG. 5: a sectional view of the closure member without the retaining ring.

Detailed description of a preferred embodiment

Fig.1 shows a longitudinal sectional view of a preferred embodiment of the present valve 10, which comprises a valve body and a generally designated manual control head 12 and 14 respectively. The valve body 12 is adapted to be screwed onto a gas cylinder (not shown) and includes a gas flow passage 16 which extends between a gas inlet port 18 and a gas outlet port 20 .

In the present embodiment, the flow passage 16 is formed by an inlet channel 22 connecting the inlet port 18 to a valve chamber 24 and an outlet channel 26 connecting the valve chamber 24 to the orifice 20. The inlet channel 22 passes through the lower part of the body 12, which is provided with a thread (not shown) allowing the valve to be screwed onto the bottle. The outlet channel 26 in turn opens into a fitting portion 28.

The end of the inlet channel 22 opening into the chamber 24 is surrounded by a first sealing seat 30 comprising an annular sealing surface with which a closure member 32 cooperates so as, depending on its axial position, to allow the flow to the outlet channel 26 or seal the inlet channel 22 in a sealed manner and thus prevent flow through the passage 16. As explained further below, the operation of the closure member 32 in the axial direction is by means of a control rod 34 of the control head 14 which is coupled to a rod portion 36 of the closure member 32 via an intermediate rod 38.

The sealing of the chamber 24 towards the control head 14 is conventionally performed by a flexible membrane 40 (plastic or metal). As seen in Figs.1 and 3, this membrane 40 surrounds the rod portion 34 and extends to the periphery of the chamber 24 where it is held by a mount 42, itself held by a tow 44 securely fixed by screwing into a bore 46 of the valve body 12.

The actuation of the shutter member is conventional and will therefore only be briefly described. The rod portion 36 comprises an outer thread by which it is screwed onto a thread of the inner surface of a housing 48 of the intermediate rod 38. The intermediate rod 38 is itself coupled to the lower end of the rod. control 34 so as to be integral with the axial displacement of the control rod, but not in rotation. The control rod 34 comprises an external thread which cooperates with an internal thread in the tow 44. A flywheel 50 is fixed to the upper end of the control rod 34. According to the direction of rotation of the steering wheel, the control rod moves up or down on the thread of the tow 44 and thus causes the axial displacement of the closure member 32 which moves towards or away from the sealing seat 30.

Referring more particularly to FIGS. 2 and 4, it will be appreciated that the closure member 32 comprises a body 33 with a free end 60 and a shoulder 62. An annular seal 64 (also called pad) of polymer material is mounted around this free end 60; the annular seal 64 has a front end face 66 facing the sealing seat 30 and a rear end face 68 resting on the shoulder 62 of the closure body 32. A retaining ring 70 circumferentially surrounds the annular seal 64 and comprises a radial rim 72 which bears on the outer edge of the front end face 66 of the annular seal 64. It will be appreciated in particular that the annular seal 64 comprises an outer annular shoulder 74 bordering its front end face 66 and that the rim 72 of the retaining ring 70 carries an annular bead 76 facing the outer annular shoulder 74 of the annular seal 64. The retaining ring 70 is attached to the closure member 32 by means of a sealed outer circumferential weld 77, so that the annular bead 76 penetrates axially into the outer annular shoulder 74 of the annular seal 64 to compress it.

The closure member 32 thus comprises an annular pellet 64 confined in an annular groove delimited by the free end 60, the shoulder 62 and the retaining ring 70 which allows a good hold of the pellet during its compression on the sealing seat 30 thus forming the main seal of the valve (in a first sealing position). Indeed, as can be seen in Fig.3, when the annular seal is pressed on the sealing seat 30 it is held well at the narrowed exit of the annular groove between the flange 72 and the end free 60.

The design of the closure member also ensures improved sealing. First, the annular bead 76 provided on the flange 72 of the retaining ring 70 overpresses the annular seal 64 in the annular groove and to occupy the entire volume. The dimensions of the annular seal 64 and the annular groove are preferably chosen so that the compression forces are initially generated by the annular bead 76 when it is put in place. This aspect will be better understood with reference to FIGS. 4 and 5. In practice, the annular seal has an initial shape (cross section) corresponding generally to that of annular groove in which will be confined after mounting of the retaining ring 70. The annular seal is then threaded on the end free 60 of the body 33 so that its rear end face 68 rests on the shoulder 62. Note the presence of a radial end projection 78 penetrating radially into an annular inner shoulder 80 of the annular seal 64, one of which functions is to hold the annular seal 64 around the free end 60 during assembly. The sharp upper edge of the radial projection 78 is provided to bite the seal 64 subjected to axial downward movement and better retain it.

Then, the retaining ring is placed on the body 33 of the closure member and then welded. To do this, it exerts on the ring an axial thrust upwards (seen in the plane of Fig.4) to bring it into abutment against the body 33 and thus penetrate the bead 76 in the shoulder 74 of the seal annular 64. It is the deformation / pressure caused by this bead during the establishment of the ring that will generate an overcompression of the seal 64 in the annular groove and force to marry completely the internal volume of the groove, thus avoiding dead volumes.

Another effect of the annular bead 76 is to punctually cause a large compression area with the annular seal 64, which forms a sealing barrier.

The welding of the retaining ring 70 is made all around the circumference of the latter so as to ensure a solid and watertight attachment to the body 33 of the closure member 32. This weld therefore closes the rear area ring seal 64, which can not be obtained with a ring screwed or crimped.

For reasons of precision and heat control, the welding is preferably carried out by means of a laser. To prevent the annular seal from being damaged by heat during welding, it is performed axially recessed relative to the shoulder 62. As seen in the Figures, the outer circumferential weld is performed at a peripheral annular shoulder 82 of the body 33 surrounding the shoulder 62 but in axial recess relative thereto. this.

Finally, a sealing barrier effect similar to that obtained at the bead 76 is also provided by the sharp upper edge of the radial projection 78 once the ring 70 is in place.

By this design, it ensures an excellent seal of the closure member 32 since the retaining ring 70 is sealed and that the two sealing barriers oppose the passage of gas towards the back of the seal 64. This configuration furthermore prevents a gas pressure from being installed at the rear of the annular seal 64 and tends to extrude the latter out of the annular groove.

Referring again to FIG. 3, it should be noted that the lower edge of the radial projection 78 is designed as an annular sealing surface 86, preferably conical, to form a second seal (metal / metal) when the seat on a second sealing seat 88 (Fig.3) surrounding the passage 16, by moving axially the closure member in a second sealing position beyond the first sealing position in which one realizes the sealing between the seal 64 and the seat 30. As can be seen, the second sealing seat 88 is surrounded by the first seat 30 and comprises a sealing surface in the form of a rounded edge.

To bring the shutter member from the first sealing position to the second sealing position, an axial displacement of less than 0.3 mm, preferably of the order of 0.1 mm, may be provided.

This second seal is particularly advantageous in that it ensures a tight seal valve, even in case of damage or even disappearance of the seal (for example following a combustion).

The annular seal is made of a polymeric material, preferably a thermoplastic polymer having low gas permeability and low creep at high pressures. The annular seal may in particular be made of: PCTFE, Vespel® (Dupont), RULON® (Saint-Gobain), PVDF.

Claims (13)

Valve, in particular for a bottle of pressurized or liquefied gas, comprising: a valve body (12) including a gas flow passage (16); a first sealing seat (30) in said gas passage (16); a closure member (32) having a free end (60) provided with a shoulder (62); an annular seal (64) mounted on said free end (60) of said closure member (32), said annular seal (64) having a front face (66) facing said first seat (30) and a rear end face (68) resting on said shoulder (62) of said obturating body (32); a retaining ring (70) circumferentially surrounding said annular seal (64) and comprising a radial flange (72) bearing on the outer edge of said front face (66) before said annular seal (64); said closure member (32) being axially movable towards said first seat (30) in a first sealing position, wherein said annular seal (64) is pressed against said first seat (30) so as to ensure a main seal of the valve; characterized in that
said annular seal (64) comprises an outer annular shoulder (74) bordering its front end face;
said flange (72) of said retaining ring (70) carries an annular bead (76) facing said outer annular shoulder (74) of said annular seal (64); and
said retaining ring (70) is attached to said closure member (32) with a sealed outer circumferential weld (77), so that said annular bead (76) axially engages said outer annular shoulder (74) of said annular seal (64) to compress it. Valve according to claim 1, characterized in that said free end (60) of said closure member (32) comprises a radial end projection (78) penetrating radially into an inner annular shoulder (80) of said annular seal (64); said free end (60) of said closure member (32) having a frustoconical shape tapering said shoulder (62) towards said radial projection (78). Valve according to claim 1 or 2, characterized in that said sealed outer circumferential weld (77) between the retaining ring (70) and the closure member (32) is made axially recessed with respect to the shoulder ( 62). Tap according to claim 3, characterized in that the closure member (32) comprises a peripheral annular shoulder (82) surrounding said shoulder (62) but in axial recess with respect thereto; and in that the retaining ring (70) is welded to the closure member at this peripheral annular shoulder (82). Valve according to any one of the preceding claims, characterized in that the sealed outer circumferential weld (77) is made by laser. Valve according to any one of the preceding claims, characterized in that said valve body (12) comprises a second sealing seat (88) surrounding said passage (16), said shutter body (32) being axially displaceable beyond said first sealing position in a second sealing position, wherein said free end (60) sits on said second seat (88) so as to achieve with it a metallic seal. Valve according to claim 6, characterized in that the first sealing seat (30) surrounds the second sealing seat (88). Valve according to claim 6 or 7, characterized in that the portion (86) of the free end (60) sitting on the second sealing seat (88) has a cross section greater than the cross section of the passage of gas at said second sealing seat (88). Valve according to claim 6, 7 or 8, characterized in that the axial displacement required to bring the closure member (32) from the first sealing position to the second sealing position is less than 0.3 mm preferably of the order of 0.1 mm. Valve according to any one of the preceding claims, characterized by a control head (14) mounted on said valve body (12) and comprising an axial control rod (34) for transmitting at least one axial actuating force to said body shutter (32). Tap according to any one of the preceding claims, characterized in that the closure member (32) comprises an axial rod portion (36) for its operation. Valve according to claim 10 and 11, characterized by a separable rigid coupling between said control rod (34) and said axial rod portion (36) of said closure member (32). Use of the valve according to any one of the preceding claims as a cylinder valve or as a gate valve in a gas distribution pipe, especially in ultra-high purity gas applications.

Images